On 106 acres in Fishlake National Forest in Richfield, Utah, a 13-million-pound giant has been looming for thousands of years. But few people have ever heard of him.

This is “the Trembling Giant,” or Pando, from the Latin word for “I spread.” A single clone, and genetically male, he is the most massive organism on Earth. He is a forest of one: a grove of some 47,000 quivering aspen trees — Populus tremuloides — connected by a single root system, and all with the same DNA.

But this majestic behemoth may be more of a David than a Goliath, suggests a study published recently in PLOS ONE. Threatened by herds of hungry animals and human encroachment, Pando is fighting a losing battle.

The study, consisting of recent ground surveys and an analysis of 72 years of aerial photographs, revealed that this unrealized natural treasure and keystone species — with hundreds of dependents — is shrinking. And without more careful management of the forest, and the mule deer and cattle that forage within him, the Trembling Giant will continue to dwindle.

“It’s been thriving for thousands of years, and now it’s coming apart on our watch,” said Paul Rogers, an ecologist at Utah State University who led the study.

Pando is constantly reproducing, which is essential to its resilience. Lacking genetic diversity, it relies on having trees of different sizes and ages. That way, if one layer or generation dies off, there’s another waiting to replace it.

But Pando’s critical demographics are out of balance. When Rogers and Darren McAvoy, a forestry colleague at Utah State, surveyed the forest, they found that older trees were dying, as expected, but that, on the whole, young ones weren’t replacing them.

Young patches of forest are at the mercy of hungry mule deer, fleeing increasing human activity. Foraging cattle, allowed into the park in the summer, are another factor in Pando’s shrinkage.

Aerial photos also revealed that Pando’s crown steadily thinned as human activity grew, with the addition of campgrounds, cabins and a telephone line, which drew grazing animals.

More fencing, culling of deer, and experimentation with the forest’s natural ecology could save Pando, Rogers said.

JOANNA KLEIN